Borehole Drilling
Cape Town

Drilling a borehole is the part of the process that most people picture, but it sits in the middle of a longer sequence. Something has to happen before the rig arrives to decide where to drill, and a good deal has to happen afterwards before you have usable water. This page covers the drilling itself: how the hole is made, what goes into it, why depths vary so much across Cape Town, and what a drilling quote should actually cover.

Borehole drilling is a geological exercise as much as a mechanical one. Two properties on the same street can need very different depths, and neither the drillers nor anyone else can see through rock. What good borehole contractors can do is read the local geology, choose the right method, construct the hole properly, and be straight with you about what is and is not predictable.

What Happens Before the Rig Arrives

Drilling without deciding where to drill is an expensive way to gamble. The steps that come first are:

1. 1Site assessment. Access for the rig and support vehicle, overhead cables, boundary walls, tree cover, slope, and where the spoil and drilling water will go. A rig is a large truck-mounted machine and cannot reach every corner of every property.
2. 2Services check. Municipal water, sewer and electrical services, septic tanks, soakaways, French drains, pool backwash lines and irrigation mainlines all need to be located and cleared before a position is confirmed.
3. 3Siting. A borehole water survey uses geophysical methods to identify the most promising position, and to rule out the least promising ones. It improves the odds. It does not guarantee water.
4. 4Regulatory position. In the City of Cape Town, boreholes must be registered with the City, and abstraction beyond reasonable domestic use may require registration or authorisation with the Department of Water and Sanitation under the National Water Act. Confirm your position before drilling, not after.
5. 5Setting the position and clearance. The exact drilling point is pegged, working space is cleared, and the sequence for the day is agreed with whoever is on site.

Cape Town Geology and What It Means for Drilling

Cape Town sits across several very different geological settings, and the setting largely determines the drilling method, the likely depth, the casing requirement and the cost. In broad terms:

Formation	Where it is typically found	What it means for drilling
Table Mountain Group sandstone	Mountain slopes and foothills, parts of the Peninsula, Helderberg and the Cape Fold belt	Hard, quartzitic and fractured. Water is held in fractures rather than pores, so yield depends on whether the hole intersects a water-bearing fracture. Hammer drilling is standard. Boreholes are often deeper here, and results between neighbouring sites can differ sharply.
Malmesbury Group shale and greywacke	Much of the northern suburbs, Durbanville, Bellville and the Swartland side	Weathered near surface and tighter with depth. Yields are frequently moderate rather than high, and the weathered zone often needs casing to keep the hole stable.
Cape Granite Suite	Parts of Paarl, Darling, Stellenbosch and sections of the Peninsula	Water occurs in the weathered mantle and in jointing near the contact zones. Depth to fresh rock varies a great deal, and drilling through the weathered zone requires care to prevent collapse.
Cape Flats sand aquifer	The sandy plain between the Peninsula and the northern and southern suburbs	An unconsolidated primary aquifer with a shallow water table. Boreholes here are usually shallower, need screened casing and a gravel pack, and are the one setting where a wellpoint may be the appropriate alternative.

Depths across the metro therefore range from relatively shallow holes in the sandy areas to substantially deeper holes in hard rock. Anyone quoting a fixed depth for your property before drilling is guessing. What an experienced contractor can give you is a realistic expected range based on nearby drilling and the local formation, plus a clear per-metre rate so the cost follows the actual depth.

Drilling Methods

• Down-the-hole (DTH) percussion hammer drilling. The standard method for hard rock in Cape Town. A compressed-air-driven hammer at the bottom of the drill string breaks the rock while air lifts the cuttings to surface. It is fast in sandstone, granite and competent shale, and the returning air and water give a running indication of what is happening below.
• Mud rotary drilling. Used in unconsolidated or collapsing formations, where drilling fluid holds the hole open. More relevant to sand and deeply weathered material than to hard rock.
• Combination approaches. It is common to start through soft overburden or weathered material with one setup, install temporary or permanent casing through it, then continue into rock with the hammer.

Typical drilled diameters for domestic and small commercial water boreholes fall in a range that accepts standard casing and a standard submersible pump. Larger diameters are used where higher yields, larger pumps or deeper casing strings are anticipated, which is more common on agricultural and industrial sites.

What Happens During Drilling

1. 1Set up and level the rig over the pegged position, with the compressor and support vehicle positioned for the run.
2. 2Drill through the overburden - soil, sand and weathered material - which is usually the least stable part of the hole.
3. 3Install and seal the upper casing through that unstable zone so the hole does not collapse and so surface water cannot run down the outside of the borehole.
4. 4Advance into rock, logging the formation from the cuttings returning to surface. This log is a useful record and you should ask for a copy.
5. 5Note water strikes. When a water-bearing fracture or saturated layer is intersected, the depth and the apparent air-lift flow are recorded.
6. 6Decide whether to continue. Deeper is not automatically better. Additional depth may add yield, may add nothing, or in some settings may reach poorer quality water. This is a judgement call made on site, and you should be part of it.
7. 7Complete the hole, install the permanent casing string and any screening, and place a gravel pack where the formation requires one.
8. 8Develop the borehole by air-lifting until the water runs clear of drilling debris and fine material, which opens up the formation around the hole.
9. 9Seal and cap. A sanitary seal at the surface and a secure cap keep contamination out of the hole.

Casing, Screening and Why Construction Matters

The hole is only half the job. What goes into it determines whether the borehole lasts and whether the water stays clean.

• Solid casing through soil, sand and weathered zones stops the hole collapsing and isolates shallow, potentially contaminated water from the deeper supply.
• Screened or slotted casing at the water-bearing interval lets water in while holding back formation material. Slot size should suit the formation, not just whatever is on the truck.
• Gravel pack in unconsolidated formations filters fine sand out before it reaches the screen, which protects the pump from abrasive wear.
• Sanitary seal and grout around the upper casing stops surface runoff, irrigation water and stormwater tracking down the outside of the casing into the borehole.
• A proper headworks and cap, raised above ground level, keeps debris, insects and contaminated surface water out.
• Casing class and material chosen for depth and formation. Casing that is too light for the depth can deform or collapse, which is expensive to remedy later.

Poor construction is the most common underlying cause of the problems dealt with on the borehole rehabilitation page. It is much cheaper to build the borehole properly than to fix it afterwards.

What Happens After Drilling

A completed hole is not yet a water supply. Three distinct things still need to happen, and they answer three different questions:

Next step	The question it answers
Yield testing	How much water can this borehole sustainably deliver, and at what pumping level? This determines pump selection and how you can use the borehole.
Water quality testing	What is actually in the water? Yield and quality are unrelated - a strong borehole can produce water that needs treatment, and a modest one can produce excellent water.
Installation	How does the water get from the borehole to where you need it? Pump, rising main, cabling, controls, storage and connection to your existing system.

What a Borehole Drilling Quote Should Cover

Drilling is normally priced per metre, which is the fairest structure for both sides given that depth cannot be known in advance. When you compare quotes, check that each one separates these items rather than presenting a single figure:

• Mobilisation and site establishment for the rig
• Drilling rate per metre, and whether the rate changes with depth or formation
• Casing supply and installation, priced per metre, with the class and diameter stated
• Screening and gravel pack where the formation requires them
• Sanitary seal, headworks and capping
• Borehole development and the time allowed for it
• The formation log and completion details you will receive
• How a dry or low-yielding hole is handled
• What is excluded - testing, pump, electrical work and connection are separate scopes

A single lump-sum figure with no depth assumption stated is difficult to compare and easy to dispute later. The borehole drilling prices page goes through the pricing structure in more detail.

Who Drills a Borehole, and Why

The reasons differ by property type, and so does the specification:

Related Borehole Services

Borehole Drilling Costs in Cape Town

Drilling is charged per metre, so the total follows the depth reached. These ranges cover the drilling scope itself - getting the hole in the ground and constructed. Testing, the pump and the rest of the system are separate scopes, priced further below on the price guide.

Item	Indicative range	What moves it
Drilling, per metre	R500 – R1,200 /m	Hard rock in the Table Mountain Group and granite sits at the upper end; sandy Cape Flats ground at the lower. Diesel cost moves this yearly.
uPVC casing, installed, per metre	R400 – R700 /m	Diameter and pressure class. Steel casing is higher again.
Mobilisation and site establishment	R2,500 – R7,500	Distance from base and how difficult it is to get a truck-mounted rig into position.
Borehole development	R2,500 – R8,000	How long air-lifting takes to run clear. Cutting this short permanently costs you yield.
Sanitary seal, headworks and capping	R1,500 – R4,000	Usually a fixed sum. Do not let it be omitted - it is what keeps surface contamination out.
Typical completed borehole, sandy shallow site	R35,000 – R70,000	Shallower holes on the Cape Flats and coastal plain, drilling plus casing and development.
Typical completed borehole, hard-rock site	R70,000 – R150,000+	Deeper holes on the Peninsula, mountain foothills and granite areas.